Voxel data sets are commonly used in computational fluid dynamic simulations. The current technique for creating voxels from BRL-CAD geometry is to use the proprietary cubit framework.
This task would involve using raytracing to interrogate a specified combination/region/assembly and produce a set of arb8's in a new region approximating the shape. Interface should be similar to the facetize command and will need the TCL binding to connect the mged editor to the library functionality.
There are tradeoffs and considerations to each of those that can be discussed in detail if you're interested.